From: Masami Hiramatsu <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org,
Tom Zanussi <tom.zanussi@linux.intel.com>,
Ravi Bangoria <ravi.bangoria@linux.ibm.com>,
Namhyung Kim <namhyung@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH 10/21] tracing/probe: Split trace_event related data from trace_probe
Date: Wed, 19 Jun 2019 10:11:33 +0900 [thread overview]
Message-ID: <20190619101133.f5aa78eac7a1cce4c24ae802@kernel.org> (raw)
In-Reply-To: <20190618122322.6875b643@gandalf.local.home>
On Tue, 18 Jun 2019 12:23:22 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Wed, 19 Jun 2019 01:14:09 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > On Mon, 17 Jun 2019 21:56:43 -0400
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> >
>
> > > > +static nokprobe_inline struct trace_kprobe *
> > > > +trace_kprobe_primary_from_call(struct trace_event_call *call)
> > > > +{
> > > > + struct trace_probe *tp = trace_probe_primary_from_call(call);
> > > > +
> > > > + return container_of(tp, struct trace_kprobe, tp);
> > >
> > >
> > > Hmm, is there a possibility that trace_probe_primary_from_call() may
> > > not have a primary?
> >
> > Good question! Of course if given event_call is not a kprobe event,
> > it doesn't have primary (or any) trace_probe. But that must not happen
> > unless user misuses it.
> > And that list never be the empty, when the last trace probe is released,
> > the event_call also unregistered and released. See unregister_trace_kprobe()
> > for details. If there is no siblings on the list, the event_call is also
> > unregistered before unregistering kprobes, and after unregistering kprobes
> > the list is unlinked.
> > (Note that unregister_kprobe() will wait a quiescence period
> > before return. This means all probe handlers are done before that.)
>
> Yeah, I thought something like that. But perhaps the
> trace_probe_primary_from_call() code should add a WARN_ON() is the list
> is empty.
OK, I'll add that, and check in all callers.
> > > >
> > > > - ret = __enable_trace_kprobe(tk);
> > > > - if (ret) {
> > > > + enabled = false;
> > > > + list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
> > > > + tk = container_of(pos, struct trace_kprobe, tp);
> > > > + ecode = __enable_trace_kprobe(tk);
> > > > + if (ecode)
> > > > + ret = ecode; /* Save the last error code */
> > > > + else
> > > > + enabled = true;
> > >
> > > So, if we have some enabled but return an error code, what should a
> > > caller think of that? Wouldn't it be an inconsistent state?
> >
> > Oops, good catch!
> > This part is related to caller (ftrace/perf) so should be more careful.
> > Usually, kprobe enablement should not fail. If one of them has
> > gone (like a probe on unloaded module), it can be fail but that
> > should be ignored. I would like to add some additional check so that
> > - If all kprobes are on the module which is unloaded, enablement
> > must be failed and return error.
> > - If any kprobe is enabled, and others are on non-exist modules,
> > it should succeeded and return OK.
> > - If any kprobe caused an error not because of unloaded module,
> > all other enablement should be canceled and return error.
> >
> > Is that OK for you?
> >
>
> Sounds good to me.
Thank you!
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2019-06-19 1:11 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-31 15:16 [PATCH 00/21] tracing/probe: Add multi-probes per event support Masami Hiramatsu
2019-05-31 15:16 ` [PATCH 01/21] tracing/kprobe: Set print format right after parsed command Masami Hiramatsu
2019-05-31 15:16 ` [PATCH 02/21] tracing/uprobe: Set print format when parsing command Masami Hiramatsu
2019-05-31 15:17 ` [PATCH 03/21] tracing/probe: Add trace_probe init and free functions Masami Hiramatsu
2019-05-31 15:17 ` [PATCH 04/21] tracing/probe: Add trace_event_call register API for trace_probe Masami Hiramatsu
2019-05-31 15:17 ` [PATCH 05/21] tracing/probe: Add trace_event_file access APIs " Masami Hiramatsu
2019-05-31 15:17 ` [PATCH 06/21] tracing/probe: Add trace flag " Masami Hiramatsu
2019-05-31 15:17 ` [PATCH 07/21] tracing/probe: Add probe event name and group name accesses APIs Masami Hiramatsu
2019-05-31 15:17 ` [PATCH 08/21] tracing/probe: Add trace_event_call " Masami Hiramatsu
2019-05-31 15:18 ` [PATCH 09/21] tracing/kprobe: Check registered state using kprobe Masami Hiramatsu
2019-05-31 15:18 ` [PATCH 10/21] tracing/probe: Split trace_event related data from trace_probe Masami Hiramatsu
2019-06-18 1:56 ` Steven Rostedt
2019-06-18 16:14 ` Masami Hiramatsu
2019-06-18 16:23 ` Steven Rostedt
2019-06-18 21:11 ` Steven Rostedt
2019-06-19 2:28 ` Masami Hiramatsu
2019-06-19 9:19 ` Steven Rostedt
2019-06-19 1:11 ` Masami Hiramatsu [this message]
2019-05-31 15:18 ` [PATCH 11/21] tracing/dynevent: Delete all matched events Masami Hiramatsu
2019-05-31 15:18 ` [PATCH 12/21] tracing/dynevent: Pass extra arguments to match operation Masami Hiramatsu
2019-05-31 15:18 ` [PATCH 13/21] tracing/kprobe: Add multi-probe per event support Masami Hiramatsu
2019-05-31 15:18 ` [PATCH 14/21] tracing/uprobe: Add multi-probe per uprobe " Masami Hiramatsu
2019-05-31 15:19 ` [PATCH 15/21] tracing/kprobe: Add per-probe delete from event Masami Hiramatsu
2019-05-31 15:19 ` [PATCH 16/21] tracing/uprobe: " Masami Hiramatsu
2019-06-18 2:16 ` Steven Rostedt
2019-06-18 16:18 ` Masami Hiramatsu
2019-05-31 15:19 ` [PATCH 17/21] tracing/probe: Add immediate parameter support Masami Hiramatsu
2019-05-31 15:19 ` [PATCH 18/21] tracing/probe: Add immediate string " Masami Hiramatsu
2019-05-31 15:19 ` [PATCH 19/21] selftests/ftrace: Add a testcase for kprobe multiprobe event Masami Hiramatsu
2019-05-31 15:19 ` [PATCH 20/21] selftests/ftrace: Add syntax error test for immediates Masami Hiramatsu
2019-05-31 15:20 ` [PATCH 21/21] selftests/ftrace: Add syntax error test for multiprobe Masami Hiramatsu
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